Fast jack liftboat shock absorbing jacking system

ABSTRACT

A shock absorbing device and system for the jacking system of a liftboat with air or cylinder chambers and manual and pressure activated control valves connecting the shock absorbing system to the hydraulic manifold of the jacking system allowing isolation or activation of the shock absorbing system. The shock absorbing system can be retrofitted to an existing jacking system. The shock absorbing device and system cushions the vessels impact with the seabed while jacking in rough seas, reducing structural fatigue and damage to the hull and jacking system. In addition, the shock absorbing device and system can broaden the liftboat&#39;s operational envelope and allow it to operate in rougher conditions without damage to the vessel.

This application claims priority from U.S. Provisional application Ser. No. 61/201,114 (“the '114 application”) filed Dec. 6, 2008. The '114 application is incorporated herein by reference.

FIELD OF THE INVENTION

This application relates to self-elevating boats known as Jack Up Boats/Jack Up Barges/Self Elevating Work Platforms or SEWOPS, used primarily in the oil and gas industry. More specifically, the present invention relates to a shock absorbing system for the jacking system of a liftboat which allows the liftboat to operate more safely and reduces the multiple impact stresses the vessel absorbs while operating in rough conditions.

BACKGROUND

In the shallow coastal waters of the Gulf of Mexico the oil industry has numerous small platforms that require maintenance and repair but have no space or facilities to accommodate the men and equipment to do the work. Trying to run a job from the deck of a floating supply boat or utility boat limited operations to the calmest of days. The need for a stable work platform that was not affected by rough seas was the catalyst for the development of the first liftboat. It was basically a barge that had long legs made of large diameter heavy pipe with a hydraulic rack and pinion drive and large pads attached to their bottom. The legs were stuck onto the sides and stern of the barge and a pair of engines were added to travel and maneuver with as well as power the hydraulic jacking system. It worked. It worked well, and the concept has spread to other parts of the world. FIG. 1 depicts an example of a current liftboat.

However, while the liftboat can operate in rough conditions once it is jacked up and has effectively become a platform, getting on location and jacking the vessel up in rough conditions is a different story. The liftboat's limitations are well known in the industry. Most operations manuals for the boats call for a limit of 4 to 5 foot seas to be able to change modes from floating operations to being jacked up out of the water. Part of the problem is the stress endured as the slow moving legs are lowered to the bottom and the wave action lifts and lowers the vessel in relation to the seabed while the legs start to come in contact with the seabed. If a vessels' legs operate at a typical 6 to 8 feet per minute and the wave period is between 6 to 10 seconds, the vessel is going to be lifted and dropped into the bottom several times before you can get your hull free of the water. You can imagine the stresses caused by hundreds of tons of steel being lifted and dropped. How serious this is largely depends on the consistency of the bottom and of course the wave height. If the bottom is soft mud it will cushion your impact but if it is hard clay or sand there are tremendous stresses imparted to the vessel and jacking system.

SUMMARY OF THE INVENTION

The design objective of this invention is to cushion the impact of the legs striking against the bottom using the energy that is fed back through the jacking system and is experienced as backpressure on the hydraulic fluid pumped to the motors. Most jacking systems are run by hydraulic motors through a planetary gear system that turns a pinion gear that drives a rack attached to the leg. The fluid does not compress, so the pinion cannot give and the impact is an uncushioned shock for the jacking machinery and the whole structure of the vessel. The present invention would utilize a compressible gas such as air to absorb the back pressure and cushion the shock by compressing and then returning the energy to the system in a controlled manner which would have obvious benefits for the vessel and machinery. This system could help buffer the shock loading of the vessel without disturbing the basic design or integrity of the proven jacking systems which are currently in use. In its simplest embodiment it is basically the addition of an air chamber of appropriate size and design integrated into the manifolds that supply the high pressure fluids to the motors and drive the jacking system. See FIG. 2. This would allow the gas to compress and decompress to absorb the energy that is fed to the pinion gear from the leg and back through the planetary to the motor and ultimately to the fluid driving the motor. In a slightly more complex version of the same invention the chamber would form a cylinder which housed a piston type shock absorber that would utilize a spring of sufficient tension to withstand the normal pressure of the jacking system without compressing. This configuration would isolate the gas from the fluid in the jacking system, which may be the preferred embodiment of the invention. See FIG. 3. Both versions of the system could use a valve that would be manually and/or pressure activated to isolate or utilize the chamber. The jacking system would operate as a conventional system until the valve was opened and the shock absorber exposed to the system's pressure variations.

This invention could be easily retrofitted to an existing jacking system to enhance its operational capabilities without compromising its strength. A liftboat which incorporated this system would have fewer stress related structural problems and could operate in higher sea states without damaging the vessel. This invention would be a welcome addition to an industry that predictably suffers from stress related maintenance problems and accidents, especially as the vessels get larger. In addition, the invention could help expand the narrow liftboat operational limitations which adversely affect the industry.

It is an object of this invention to provide a shock absorbing device and system of operation that can be incorporated into a liftboat's hydraulic jacking system to cushion the vessels impact with the seabed while jacking in rough seas thereby reducing structural fatigue and damage to the hull and jacking system.

It is a further object of this invention to provide a shock absorbing device that can broaden a liftboat's operational envelope and allow it to operate in rougher conditions without damage to the vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an outboard profile of a typical liftboat as known in the prior art.

FIG. 2 is a schematic drawing of one embodiment of the inventive shock absorbing device.

FIG. 3 is a schematic drawing of an alternate embodiment of the inventive shock absorbing device.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts an outboard profile of a typical liftboat as currently known in the art. Shown is the hull 1, the legs 2, the pads 3, the jacking towers 4, while the actual jacking system is not shown.

FIG. 2 shows a schematic of one embodiment of the inventive shock absorbing device 5 mounted on the hydraulic manifolds 7 of a jacking system mounted on each leg 2 of a liftboat. Shown are the multiple motors 9 connected to planetary gears drives 10, with hydraulic hoses 8 connecting the motors 9 to the hydraulic manifolds 7. The shock absorbing device 5 is connected to the hydraulic manifolds 7 with control valves 14 controlling flow between the hydraulic manifolds 7 and the air chambers 6.

FIG. 3 shows a schematic of an alternate embodiment of the inventive shock absorbing device 5 mounted on the hydraulic manifolds 7 of a jacking system mounted on each leg 2 of a liftboat. Shown are the multiple motors 9 connected to planetary gears drives 10, with hydraulic hoses 8 connecting the motors 9 to the hydraulic manifolds 7. The shock absorbing device 5 is connected to the hydraulic manifolds 7 with control valves 14 controlling flow between the hydraulic manifolds 7 and the cylinder chambers 11. In the cylinder chambers 11 are pistons 12 and springs 13. In this embodiment the gas would be isolated from the fluid used in the jacking system. It is understood that the gas used in either air chamber 6 or cylinder chambers 11 could be any suitable gas and is not limited to air.

While not depicted, it is understood that the shock absorbing device 5 is mounted on the jacking system is mounted on each leg 2 of the liftboat, each of which legs 2 are fitted with a rack engaged by pinions driven by the planetary gear drives 10.

It is also intended that in all embodiments of the shock absorbing device 5, the control valves 14 could be manually or pressure activated to isolate or utilized the air chamber 6 or the cylinder chambers 11. The jacking system would operate as a conventional system until the valves 14 were opened and the shock absorbing device 5 exposed to the jacking system's pressure variations. 

1. A shock absorbing device for a liftboat jacking system with a hydraulic manifold comprising at least one air chamber connected to the hydraulic manifold by at least control valve.
 2. The shock absorbing device of claim 1 wherein the control valve is manually controlled.
 3. The shock absorbing device of claim 1 wherein the control valve is pressure activated.
 4. A shock absorbing device for a liftboat jacking system with a hydraulic manifold comprising at least one cylinder chamber with a piston and a spring connected to the hydraulic manifold by at least control valve.
 5. The shock absorbing device of claim 4 wherein the control valve is manually controlled.
 6. The shock absorbing device of claim 4 wherein the control valve is pressure activated. 